Automatic telephone-exchange system



Aug. 5, 1930. w c zET AL 1,772,235

AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed March 9, 1929 .QiM/Mcran 3. J ohnSsa V7 12v V To 125 Patented Aug. 5, 1930 UNITED STATES PATENT OFFICE KARL FREDRIK WINCRANTZ AND KARL GEORG JOI-INSSON, OF STOCKHOLM, SWEDEN, ASSIGNORS TO TELEFONAKTIEBOLAG ET L. M. ERICSSON, GF STOCKHOLM, SWEDEN,

A COMPANY OF SWEDEN AUTOMATIC TELEPHONE-EXCHANGE SYSTEM 7 Application filed March 9, 1929, Serial No. 345,763, and in Sweden March 6, 1928. I

The present invention refers to such automatic telephone exchange systems in which the incoming ,traific from a central station is attended to'and supervised at a local exchange by operators who receive the calls and establish the desired connections through the local automatic exchange on the principles of a semi-automatic system. More particularly,

the invention relates to a simplified semi- 10 automatic system especially adapted for small automatic telephone plants, such as private branch exchanges. The object of the invention is to provide semi-automatic working without the necessity of arranging special switch-boards for this purpose at the automatic station. This is rendered possible according to the invention by one or more of the telephone apparatus connected tothe exchange being arranged to mediate the trafi'ic coming from the central station. These apparatus, which preferably are of the common desk set type, are only provided with the signalling devices and switching means required for the handling of the trafiic, such as call and supervisory lamps, keys, manual switches, or the like, and an impulse transmitter, whereas the switching devices required for the connection of the telephone apparatus to the different junction lines are arranged.

at the automatic exchange. The'latter devices may consist, for instance, of relays adapted to be actuated from the telephone apiparatus by means of keys, switches or, the li e.

The invention furthermore aimsat facilitating an occasionaldistribution of the traffic onto two or more apparatus,the calls being normally received at a main apparatus, however, which is provided with switching 40 devices for the purpose of transferring of one or more calls to an auxiliary apparatus, when the trafiic is heavy, so that these calls may be handled at thelast mentioned apparatus; I

The invention will be described more closely with reference to theaccompanyingdrawlngs, which illustrate two telephoneapparai tusA and A intended for the handling of the trafiic received at a private branch exchange, together with appertaining signalling and switching means. The apparatus A is the'main apparatus to which all calls are normally directed, whereas the apparatus A is an auxiliary apparatus capable of taking charge of a portion'of the traflic when required. The parts pertaining to the apparatus A are disposedunderneath thechain dotted line H inth'e drawing, whereas the parts pertaining to the auxiliary apparatus A are disposed above the chain dotted line,

H The parts situated between these lines are switching devices pertaining to the apparatus A and A and to the main lines'entering from the central station, andwhich are disposed at the automatic exchange proper;

In the drawing, only one main line HL is shown, but a number ofsuch lines may obviously be arranged in an analogous manner.

A selector V connected to the main line HL and'with appertaining switching means is shown to the right'of the vertical chain dotted. line H The main apparatus A andthe, auxiliary apparatus A areof the desk set type. They I are provided with a micro-telephone compr s'-.- ing a head phone T and T respectively, and

a micro-phone M and M respectively, afin- ,ger dial D and D respectively, a hook switch H0 and H0 respectively, two signal lamps main apparatus A is. provided with' keys KBK, MBK and KK, which are common to all main lines. Disregarding the. special means for handling the incoming traflic, the

apparatus A A are equivalent to the. other apparatus connected to the automatic exchange. Thus, they may be disposed'in any suitable places Within the ware house or the like to be served by the exchange. The nature of the other devices Will be apparent from the description of the switching operation hereinbelow. I

The central station may be a manual or an automatic station but is assumed in the following to be a manual station. On a call from the rnain station a call relay IR is actuatedhy means of alternating currentover the line circuit 1 containing a winding 3. on the said relay connected between the. two line branches L L over a condenser 2. When the relay IR attracts its armature, a holding circu-it for another winding 5- on the call relay is closed. Furthermore, a current path 6 is closed through a call lamp, AL at the main apparatus A11 When the operator sees the lamp A lighting up she clepresses the keySK of the'correspo nding line HL {o a mom nt, a ircuit 7 ei g hus clo ed; aidcircui ol ilaini g t eay Al a, BB1. nd a es t nc R1 he, re lay A,R receives. holding current over a circuit, 8 containing a resistance and a co n tact 9' on the operators hook switch. H0 w ich at rcontact isv broke w e h 1 erators, microphone is hooked. .on.. Moreover, the relay AR .closesacircuitlO through. a s ow-ac ing el y GB; whi h h n a t a ts s a ma r 'an @bnne ts'the line HL-to he telephone apparatus A1. overback contacts. n a s i ting re ay B1... The h ldin circui for the relay IR is then brokenqat the am time, hus. cau i g. h all lamp AL.-

go-outur.ther no :e,. he elay Rs-c e a cu r nt pa h 11 for. a ontr l la -p. KLl. ft r he pe ator hashee i f rme o the um er esir d, she depr theSQIf odG ing key DKM,wherebyv the relay DR is ener-l giz lh atte elay hif t e .op a speaking CiIicui-t fromthe outer line to the end of the line entering the automatic change, a circuit 12 being thus closed. over pe ating on actson he previously a tuated.

mitten D1, o he p ation. Wh n DB1 atra ts its arma ur thetw line ranch s L1, L2; areun tedi over a ontact wher y he ne. rc i s ept osed- Moreo er,. a; circuit 14 is formed whichcontai-nsa nelay. ER h ch now a trao sitsarma r and,;i-nurm, closes a circuitover the coiliilht 1-5.: d hirough he esis nce 'hd ti s the relay ER closes; a branch, circuit to the n ro lamp- KLl at he. on a t: 1 h ayr lay R; tur hermorecloses. a c i .7. h ough. a re ay PR witching i s i 'I o ho f lilhgoirceit. oy n i cont ct 1-8 hil at s me. ime; closing a circui for the inding 29, qfa relay OR at; conta t. 19 h l er nlay then wit hes its. econd; Wmdma 21 into aho di heqircuit.22.; et he same he. circuit illt r. heafl x 3R6 external line;

. relay. HR connected between ay BB1. ancl throngh a. line relay LB... The. latter'circuit also contains the impulse transis interrupted, which in turn interrupts the circuit for the operating winding 20 on the relay OR. Furthermore, the relay OR closes a branch circuit to the relay GB at the contact 28. Moreover, the relay OR closes the circuit for a slow-acting relay NR at the contact 24', which latter relay in turn connects an inductive resistance RD to the line branch L When the line relayLB attracts its armature, an impulse circuit 25 is closed through the driving magnet DM of the selector V, said impulse circuit containing an impuls machine TM. Thus'theselector will; be driven step by step until it'iinds an unoccupied trunk line, when a. test circuit 26 is closed through the one winding 21 of a stop relay SR which 'now attracts its armature and breaks the arm K of the selector, itscontacts 29, 30;

the relay SR furthermore connects theline HL to the trunk line in. questi-onover the I contact arms K K, of the selector When the line has thus obtainediconnection with the impulse receiver of the automatic ex change the operator in known manner recelves a buzzer signal, whereupon theimpulse transmitter D may be: actuated to establish the connection over the automat c exchange.

As soon the operator has. completed the connection and. satisfied herself oi? the tact.

ator may disconnect herself from the connect thatthe called line is not engaged,. the .opertion by'pulling up the keyrDK ithe relay.

DB then releasing its armature and again. connect ng the operators speaking. set to! the hooks on her microtelephone, the current When the operator finally j path 8, is interrupted the, relays. AR- and BB thus releasing their armatures. an d, completing the connection. The supervising circuit of'the main line isnow kept closedjbyr the line branches... Before: the called. subscriber swers, the connection. is maintainediover the, V

automatic exchange through, a branch o t the; circuit 12 over the r'esistanceRD. The con-.

dGIlSers 31, 32 inserted into, thespeaking cir-- cuit separate the direct current, circuits. from; I

each. other. 1

Vilhen the calledv subscriber answers,,a. ci rcuit 33 isestablished over the line of the called subscriber. and through relay GR,

which. now "attracts: its. armatu-Ee and breaks.

the circuits. 14, 15, the, short circuit ot the cuit 85. containing the second. winding; 36. at

theJrelay... At the. same time the. circuit interrupted tor the relay r ER, which} in turn.

interrupts the circuit for the winding 34 the, relay EH When the; Elam EB. is.- do" When, on the termination of the conversa-.

tion, the called subscriber hangs up his microtelephone, the circuit 33 containing the relay CR is broken, which relay is now de-.

energized so as to interrupt theholding circuit for the relays OR and FR. When OR is deenergized, the circuit is interrupted for therelay GR, wherebythe main line is disconnected. lVhen OR is deenergized, also the relay NR releases its armature, whereby the holding circuit-from RD over the line branch L andthrough LB is broken, causing the automatic connection to be interrupted in known manner.

'In case of the called subscriber failing to answer, which is evidenced by the control lamp KL remaining alight, the operator may again switch herself into the connection by depressing the key SK the relays AR and BR being then again rendered operative in the manner previously described. Thus the operator is again in connection with the external line and may communicate with the calling subscriber. The operator may then interrupt the connection by depressing the key BK which closes a circuit 33 for therelay GR, which will have the same result as if the called subscriber answered. When the operator releases the key BK anew, thelatter circuit is interrupted and the relay GR is deenergized, all relays'on the automatic side being then deenergized in the manner previously described. When the operator then hooks on her microtelephone, the circuit for the relays AR and BR is interrupted, whereby the connection with the central station is interrupted in the manner previously described. I

If the called subscriber is occupied, which is indicated by a tone in the head-phoneof the operator, the operator 'may break the connection byactuating the keyBK in the manner just described,

In order to facilitate the work'of the operator in periods of heavy traffic, arrangements are provided tomake it possible for the operator to disconnect her apparatus from-the line, without it being necessary for thispurpose to hook on her microtelephone. The

said arrangements are such that the discon nection of the-telephone apparatus takes place automatically when the operator, for

the purpose of answering a call on another line, actuatesthe key SK pertaining to said line, a branch being then established to the circuit 8 at the common point 38 over the circuit 7 andthe appertaining answering key SK of the line last calling. By reason of the large resistance R contained in the circuit 8 the latter circuit now receives so small a current that'its relays AR and BR releasetheir 'armatures, the circuit 8 being thus interrupted. 1 r

On a call from the automatic telephone exchange to the central station a current path 39 is established, said path containing the line relay LB and afrelay RR. -Theline relay starts the selector Vin the manner pre-. viously described and establishes a test circuit through the winding 27 on the relay SR and over a fourth contact arm K on the selector. When the selector finds the calling circuit, the operating circuit 25 is broken in the manner previously described, by the relay SR being rendered operative. Hereby the line of the calling subscriber is switched on to the main line HL, the relay CR then receiving current. in the manner previously described. When CR attracts its armature, the circuit for the relay PR is closed at the contact'40. PR attracts its armature and closes the circuit through the winding 20 of the relay OR, the latter relay in turn closing the contact 23 and thus actuating the relay GR which completes the connection to the main line. Normally, the outgoing traffic is thus effected altogether automatically without the aid of any operator.

By depressing the key KK the operator T at the apparatus A may at any time find out which main lines HL are occupied by conversations, the circuits for the appertaining control lamps KL being then closed over the contact on the relays GR and HR.

When leaving her place the operator at the apparatus A may transferthe handling of the traffic to the operator at the apparatus A by depressing the self-locking key KBK. This results in that a relay KR brought into operation, said relay preparing the switching-in of the calllamps AL of the ap paratus A while the control lamp KL is shunted to the control lamp KL The call lamp AL then assumes the function of the lamp AL in such manner that, when the relay IR attracts its armature by reason of a call, the lamp circuit is closed over-anontact 41 on the relay KR.- fAt the same time the relay TR is brought into operation, whereby the'lamp AL is disconnected. The operator at the apparatusA may then carry out the same functions which have been described hereinbefore with reference to the apparatus A the operator at A making use, however, of a set of relays AR BB and DR which relays operate in a manner'entirely analogous to that of the corresponding relays AR BR and DR vThus the relays AR and BR serve to facilitate connection of the apparatus A to the one or the other side of the connection, whereas the relay DR controls shifting of the apparatus to the one or the other side. The key 8K aswell as the keys BK and DK serve the pose.

and SK the relays TR are actuated for themain lines in qu-estion,inthat the'circuit' of there-lay TR is then closed over a contact 42 on the relay MR. Hereby'the circuit of the call'lamps is switched over' from the appa-' rat us A onto the apparatus A2 in themannerpreviously described, whereupon the operator at theapparatus A can attend to the desired connections.

opera-tor at A remains with the operator at A inasmuch as the control lamps KL have not been switched in. Said switching over of calls may also be efiectedby a momentary actuation of the key KBK, all unanswered calls beingthen switched over, without any key SK having to be actuated for this pur- By arranging a plurality of keys KBK, corresponding to different groups of incomingmain lines, the operator may switch over an arbitrarygroup of lines onto the assistant operator at will. 7 L

The'apparatus A and A may also receive calls-from other apparatus in the automatic 1 exchange,fand are for this purpose connected to the exchange similarly as other apparatus. If required, the operator at the'main apparatus A may assist in establishing connec tions over the central stat-ion, for instance in the case of long distance service connections,

the operator then getting into communication with the station by depressing akey SK on 'having first convinced herself, by depression of the control key KK, that the main line in'question is unoccupied.

The apparatus A and A are thus to be regardedas' ordinary subscribers stations in the automatic exchange, and they are also intended to be used as such,for instance by the staff of an office or a warehouse; At-the same time, however, they may also be served by the same stafi in the manner above de-- scribed, to mediate, incoming as well as out-- going traffid We claim V 1. In a telephone system a-main ofiice, a branch office comprising an automatic exchange,main lines connecting the main oifice with the branch'oifice and terminating in the automatic exchange, subscribers telephone lines terminating in the automatic exchange, subscribers stations having telephone apparatus associated witlisaid subscribers lines,

one of'said subscribers apparatus'being provid'ed wi-th means for mediatingthe incoming In this case, however, the controlover the connections set up by the traflic from the main oific'e comprising switch ing means at the automatic exchange for connecting the telephone lineof the mediating subscribers apparatus with each of said main lines, circuits for said switching means, keys on the mediating apparatus for operating said switching means over said circuits, and call indicating means on the mediating ap-' paratus for indicating calls from the main oliice, p I

2. In a telephone system a main oiiice, a branch ofiice comprising an automatic ex-- change, main lines connecting the main ofiice with the branch office and terminating in the automatic exchange, subscribers telephone lines terminating in the automatic exchange,

subscribers stations having telephone apparatus associated with said subscribers lines, one of said subscribers apparatus being provided with means for mediating the incoming traiiic from the main office comprising switching means at the automatic exchange for connecting the telephone line of the mediating subscribers apparatus with each of said main lines, circuitsfor said switching means, keys on the mediating apparatus for operating said switching means over said circuits, call indicating means on the mediating apparatus, and means for connecting a' main line with a subscribers line through the automatic exchange under the control of the mediating apparatus.

3. In a telephone system a main office, a

branch office comprising an automatic exchange, main lines connecting the main oflice with the branch office and terminating in'the automatic exchange, subscribers telephone lines terminating the automatic exchange, I

subscribers stations having telephone apparatus associated with said subscribers lines;

two of said subscribers apparatus, hereinafter called main apparatus and auxiliary apparatus, being each provided with means for mediating the incoming traflic from the main ofiice comprising switching means at the automatic exchange for connecting the telephone line of the mediating subscribers apparatus with each ofsaidmainlines, cir-- cuits for said switching means, keys on the mediating apparatus for operating said switching means over'said circuits, call indicating means on the mediating aparatus for indicating calls from the main oflice and circuits for said call indicating means, and

' means under the control of the main apparatus for shifting said circuits so as to transfer. the calls from the main apparatus to the auxiliary apparatus; 7 l

4. A telephone system as claimed in claim 3, in which the means for transferring calls from the main apparatus to the auxiliary apparatus comprise keys individual to the main lines and controlling the call indicating-coir cuits so as to allow of calls on any mainline to be transferred separately to the auxiliary apparatus.

5. A telephone system as claimed in claim 3, in which the means for transferring calls from the main apparatus to the auxiliary apparatus comprise a key on the main apparatus and a relay at the automatic exchange arranged under the control of said key and adapted to control the circuits of all the call indicating means so as to transfer all the calls to the auxiliary apparatus on operating said key.

In testimony whereof we aflix our signatures.

KARL FREDRIK WINGRANTZ. KARL GEORG JOHNSSON. 

